Subsurf Modifier artifacts
You have some non-manifold geometry in your mesh.



There is a large ngon overlapping the other polygons.



Here is how to fix it:


Select the large ngons


you can either do this manually which is faster in this case since there are only 2 ngons or you could use a selection tool.
Select -> Select Faces by sides: greater than 4

Delete them: x -> Faces (3)
Select all geometry in the mesh: A
now to fix the holes: Mesh -> Clean Up -> Fill Holes






This fixes part of your problem. The other problem is the creasing. To fix this I would either use edge loops instead of creases or crease all continuous parts of the mesh rather than just single edges.